Retort adhesive composition

ABSTRACT

A solvent-based polyurethane retort adhesive composition for producing laminates including: (A) at least one isocyanate compound, Component A; and (B) at least one isocyanate (NCO)-reactive component, Component B, comprising (i) at least one phosphate ester compound and (ii) at least one polyester polyol having an average molecular weight of greater than 3,000 g/mol; a process for producing the above adhesive; a multi-layer laminate product including the above adhesive; and a process for producing a laminate product using the above adhesive.

FIELD

The present invention relates to a retort adhesive composition useful ina laminating process; and the preparation of such retort adhesivecomposition. More specifically, the present invention relates to asolvent-based retort adhesive composition for use with laminate films,the adhesive composition exhibiting regulatory compliance, fast curingand good adhesion performance; and a process of making the same.

BACKGROUND

Adhesive compositions are useful for a wide variety of purposes. Forinstance, some adhesives are used to adhere two or more film layers ofsubstrates together thereby forming composite films, i.e., laminatescomprising the two or more film layers. Example of substrates typicallyinclude polyethylenes, polypropylenes, polyesters, polyamides, metals,papers, or cellophane and the like. The use of adhesives in differentlaminating end-use applications is generally known. For example,adhesives, are generally applied between laminating films, can be usedin the manufacture of film/film and film/foil laminates used in theflexible packaging industry for packaging of foodstuffs,pharmaceuticals, and industrial consumables, especially for foodpackaging. Laminating adhesives can be classified generally into threecategories: (1) solvent-based laminating adhesives, (2) solventlesslaminating adhesives, and (3) water-based laminating adhesives. Theperformance of an adhesive varies by category and by the application inwhich the adhesive is applied. Within the solvent-based category oflaminating adhesives, solvent-based polyurethane has been widely used toachieve relatively good heat, moisture, and chemical resistance.

Within the category of solvent-based laminating adhesives, there aremany varieties; and one particular variety includes multi-componentpolyurethane-based laminating adhesives; and more specifically atwo-component adhesive. Typically, a two-component polyurethane-basedlaminating adhesive includes a first component comprising an isocyanateand/or a polyurethane prepolymer and a second component comprising oneor more polyols. A polyurethane prepolymer can be obtained by thereaction of a polyisocyanate with a polyether polyol and/or polyesterpolyol. The second component comprises polyether polyols and/orpolyester polyols. Each component can optionally include one or moreadditives. Common solvents used in such systems include methyl ethylketone, ethyl acetate, toluene and the like, all of which must bemoisture-free to prevent premature reaction of the isocyanate groups ofthe polyurethane.

The two components (i.e., the isocyanate and polyol components) of theadhesive composition are combined in a predetermined ratio, therebyforming an adhesive composition. The adhesive composition, carried in asolvent, is then applied on a film/foil substrate. The solvent isevaporated from the applied adhesive composition. Another film/foilsubstrate is then brought into contact with the other substrate, forminga curable laminate structure. The laminate structure is cured to bondthe two substrates together.

Solvent-based adhesive compositions can be used in high-performancelaminate applications (e.g., retort, hot-fill, boil-in-bag, etc.). Forexample, in retort flexible packages applications, the retort flexiblepackages offer several benefits, such as (1) consumer convenience, (2) along shelf life of food packed in the packages, and (3) preservation ofthe original flavor of the packed food. Retort flexible packages such asretort pouches are commonly constructed with multilayer laminationstructures, such as a three-ply structure or a four-ply structure. Thethree-ply structure generally includes, for example, an outside layer ofpolyethylene terephthalate (PET), a middle layer of a metal foil (e.g.,aluminum), and an inside layer of casted polypropylene (CPP); and thethree-ply structure is generally indicated as PET//Foil//CPP. Thefour-ply structure generally includes, for example, an outside layer ofPET, a first top middle layer of a metal foil, a second bottom middlelayer of Nylon, and an inside layer of CPP; and the four-ply structureis generally indicated as PET//Foil//Nylon//CPP. A laminating adhesiveis applied to the structures to bond the different layers together. Thelaminating adhesives used for retort flexible package applications mustnot only meet the extreme performance requirements at high temperaturein the presence of highly acidic and fatty food, such as at atemperature of 121 degrees Celsius (° C.) for 1 hour (hr) or 132° C. for30 minutes (min); but the laminating adhesives must also meet verystrict regulatory standards such as the regulations promulgated by theFederal Department of Administration (FDA) and the European Union (EU).

There are basically four kinds of known retort adhesives. Two adhesivesare based on an aliphatic isocyanate, which meet regulatory compliance,but the curing of such aliphatic-based isocyanate adhesives is veryslow, and the adhesives have performance issues. The other two types ofadhesive contain aromatic isocyanates; and such aromatic-basedisocyanate adhesives have fast curing but such adhesives do not meetregulatory compliance for retort applications and the adhesives alsohave performance issues. The prior art does not disclose an “all-in-one”retort adhesive which meets regulatory compliance, has a fast curingproperty, and has good adhesion properties for retort applications.

For example, the known laminating adhesives for retort applications: (1)exhibit good adhesion performance for a wide range of retort substratesand structures, and the adhesives are generally compliant with globalfood regulations for retort applications; but the adhesives exhibit aslow curing property, such as being curable above 40° C. for at least 10days, before packaging foodstuff in packages made using the knownlaminating adhesives; or (2) are generally compliant with global foodregulations for retort applications; but the adhesives exhibit a slowcuring property, such as being curable above 40° C. for at least 10days, before packaging foodstuff in packages made using the knownlaminating adhesives; and the adhesives do not exhibit good adhesionperformance for a wide range of retort substrates and structures; or (3)exhibit a fast curing property, such as being curable at ambientconditions in 10 days or at an evaluated temperature (e.g., greater thanor equal to (≥) 40° C.) in five days; and the adhesives exhibit goodadhesion performance on typical retort substrates and structures; butthe adhesives are generally not compliant with global food regulationsfor retort applications, for example, the adhesives have issuescomplying with FDA and EU regulations. It is also known thataromatic-based adhesives do not exhibit good adhesion performance.

It is therefore desirous to provide a retort adhesive that, not onlyexhibits excellent adhesion performance, heat resistance, and chemicalresistance; but also exhibits a fast curing characteristic (i.e., acuring time of less than [<] eight days) at ambient curing conditionsand a curing time of <five days at an evaluated temperature (e.g., ≥40°C.). At the same time, it is desirous to provide a retort adhesive thatmeets regulatory compliance. For instance, adhesives containing aromaticpolyisocyanates such as methylene diphenyl diisocyanate (MDI) andtoluene diisocyanate (TDI) can produce primary aromatic amines such asmethylene diphenyl diamine (MDA) and toluene diamine (TDA) that areundesirable and can potentially migrate into food from the adhesive.Generally, to be in compliance with typical government regulations, theregulations require that the total amount of migrated aromatic aminessuch as MDA and TDA, into food packed in packages using retort adhesivesneed to be very low, for example, in the parts per billion (ppb) levelto be in compliant with FDA and EU food regulations, after the adhesivesare subjected to severe retort testing conditions.

SUMMARY

In the present invention a novel solvent-based adhesive is disclosedwhich exhibits the desired performance attributes and solves theproblems of the previously known adhesives used for retort applications.In one embodiment, the present invention is directed to amulti-component (e.g., a two-component), solvent-based polyurethaneretort adhesive composition for producing laminates including anisocyanate component, Component A, and an isocyanate group (NCO)reactive component, Component B. In a preferred embodiment, the adhesivecomposition includes, for example: (A) at least one isocyanate compoundas Component A; and (B) at least one isocyanate group (NCO) reactivecomponent as Component B; wherein the at least one isocyanate reactivecomponent includes (i) at least one phosphate ester compound and (ii) atleast one polyol comprising a polyester polyol having the appropriatemolecular weight distribution such as having an average molecular weight(Mw) of greater than or equal to (≥) 3,000 grams per mole (g/mol).

In another embodiment, the at least one isocyanate compound of theadhesive composition includes, for example, at least one aliphatic-basedisocyanate.

In still another embodiment, the at least one isocyanate compound of theadhesive composition includes, for example, a blend of (i) at least onearomatic-based isocyanate and (ii) at least one aliphatic-basedisocyanate.

In other embodiments, the present invention includes a process forproducing the above adhesive; a multi-layer laminate product includingthe above adhesive; and a process for producing a laminate product usingthe above adhesive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graphical illustration showing an attenuated totalreflectance (ATR) of inventive and comparative samples after 3 dayscuring at an elevated temperature of 50° C.

DETAILED DESCRIPTION

The numerical ranges disclosed herein include all values from, andincluding, the lower and upper value. For ranges containing explicitvalues (e.g., a range from 1, or 2, or 3 to 5, or 6, or 7), any subrangebetween any two explicit values is included (e.g., the range 1-7 aboveincludes subranges 1 to 2; 2 to 6; 5 to 7; 3 to 7; 5 to 6; etc.).

The term “composition” refers to a mixture of materials which comprisethe composition, as well as reaction products and decomposition productsformed from the materials of the composition.

The terms “comprising,” “including,” “having,” and derivatives of theseterms, are not intended to exclude the presence of any additionalcomponent, step or procedure, whether or not the same is specificallydisclosed. In order to avoid any doubt, all compositions claimed throughuse of the term “comprising” may include any additional additive,adjuvant, or compound, whether polymeric or otherwise, unless stated tothe contrary. In contrast, the term “consisting essentially of” excludesfrom the scope of any succeeding recitation any other component, step,or procedure, excepting those that are not essential to operability. Theterm “consisting of” excludes any component, step, or procedure notspecifically delineated or listed. The term “or,” unless statedotherwise, refers to the listed members individually as well as in anycombination. Use of the singular includes use of the plural and viceversa.

An “isocyanate” is a chemical that contains at least one isocyanategroup in its structure. An isocyanate group is represented by theformula: —N═C═O or abbreviated as “NCO”. An isocyanate that containsmore than one, or at least two, isocyanate groups is a “polyisocyanate.”An isocyanate that has two isocyanate groups is a diisocyanate and anisocyanate that has three isocyanate groups is a triisocyanate, etc. Anisocyanate may be aromatic or aliphatic.

A “polyisocyanate” is a molecule that contains at least two isocyanategroups.

A “polyether” is a compound containing two or more ether linkages in thesame linear chain of atoms.

A “polyester” is a compound containing two or more ester linkages in thesame linear chain of atoms.

A “polyol” is an organic compound containing multiple hydroxyl (OH)groups. In other words, a polyol contains at least two OH groups.Nonlimiting examples of suitable polyols include diols having two OHgroups, triols having three OH groups, and tetraols having four OHgroups.

A “polyester polyol” is a compound that contains a polyester and apolyol in the backbone structure of the compound.

A “polyether polyol” is a compound that contains a polyether and apolyol in the backbone structure of the compound.

A “film,” including when referring to a “film layer” in a thickerarticle, unless expressly having the thickness specified, includes anythin, flat extruded or cast thermoplastic article having a generallyconsistent and uniform thickness of about 0.5 millimeters (mm) (20 mils)or less in one dimension.

A “polymer film” is a film that is made of a polymer or a mixture ofpolymers. The composition of a polymer film is typically, 80 percent byweight (wt %) of one or more polymers.

A “polymer” is a polymeric compound prepared by polymerizing monomers,whether of the same or a different type. The generic term polymer thusembraces the term “homopolymer” (employed to refer to polymers preparedfrom only one type of monomer, with the understanding that trace amountsof impurities can be incorporated into the polymer structure), and theterm “interpolymer,” which includes copolymers (employed to refer topolymers prepared from two different types of monomers), terpolymers(employed to refer to polymers prepared from three different types ofmonomers), and polymers prepared from more than three different types ofmonomers. Trace amounts of impurities, for example, catalyst residues,may be incorporated into and/or within the polymer. It also embraces allforms of copolymer, e.g., random, block, etc. It is noted that althougha polymer is often referred to as being “made of” one or more specifiedmonomers, “based on” a specified monomer or monomer type, “containing” aspecified monomer content, or the like, in this context the term“monomer” is understood to be referring to the polymerized remnant ofthe specified monomer and not to the unpolymerized species. In general,polymers herein are referred to as being based on “units” that are thepolymerized form of a corresponding monomer.

It is well established in the art of adhesives that to make a two-partadhesive system includes providing a first part comprising anisocyanate-containing component (herein Component A); providing a secondpart comprising an NCO reactive component such as a polyol component(herein Component B); and then combining or mixing Component A andComponent B to form the two-part adhesive system or composition.

In one broad embodiment, the present invention is directed to asolvent-based polyurethane retort adhesive for producing a laminateincluding a Component A comprising at least one isocyanate-containingcompound; and a Component B comprising at least one NCO reactivecomponent; wherein the at least one NCO reactive component contains (i)at least one phosphate ester compound and (ii) at least one polyolcomprising at least one polyester polyol having an average Mw of ≥3,000g/mol. The phosphate ester polyol in the at least one NCO reactivecomponent can be present in a concentration of, for example, from 0.1 wt% to 30 wt % in one embodiment. In a first preferred embodiment, the atleast one isocyanate compound of the adhesive is, for example, at leastone aliphatic-based isocyanate. In a second preferred embodiment, the atleast one isocyanate compound is a blend of (i) at least onearomatic-based isocyanate and (ii) at least one aliphatic-basedisocyanate. In the second preferred embodiment, the at least onearomatic-based isocyanate can be an isocyanate prepolymer comprising areaction product of (i) at least one polyisocyanate and (ii) at leastone polyester polyol having a Mw of ≥3,000 g/mol.

The unique adhesive of the present invention has several advantages overthe heretofore known solvent-based polyurethane retort adhesive systemsincluding, for example, (1) good adhesion performance; (2) a fast curingproperty; and (3) either (a) no level of aromatic amine migration or (b)a very low level of aromatic amine migration. The unique solvent-basedpolyurethane retort adhesive system, in turn, is useful in a process ofmaking a laminate having good heat resistance and good chemicalresistance for use in making a retort packaging article.

As aforementioned, the at least one isocyanate-containing compound,Component A, used to make the adhesive is, for example, at least onealiphatic-based isocyanate in one embodiment; or the at least oneisocyanate compound used to make the adhesive is, for example, a blendof (i) at least one aromatic-based isocyanate and (ii) at least onealiphatic-based isocyanate in another embodiment. Theisocyanate-containing compound useful in the present invention can beselected, for example, from the group consisting of an isocyanatemonomer, a polyisocyanate (e.g., dimers, trimmers, etc.), an isocyanateprepolymer, and mixtures of two or more thereof. As used herein, a“polyisocyanate” is any compound that contains two or more isocyanategroups.

Further, the isocyanate-containing compound can be selected from thegroup consisting of aliphatic polyisocyanates, cycloaliphaticpolyisocyanates, aromatic polyisocyanates, and combinations of two ormore thereof. An “aliphatic polyisocyanate” is a polyisocyanate thatcontains no aromatic rings. A “cycloaliphatic polyisocyanate” is asubset of aliphatic polyisocyanates, wherein the chemical chain isring-structured. An “aromatic polyisocyanate” is a polyisocyanate thatcontains one or more aromatic rings.

The aliphatic-based isocyanate component useful in the presentinvention, as Component A, can include one or more compounds including,for example, aliphatic polyisocyanates having 3 carbon atoms (C) to 16 Cin one embodiment, and 4 C to 12 C in another embodiment, in the linearor branched alkylene residue. Also suitable for use in the presentinvention are cycloaliphatic polyisocyanates including, for example,cycloaliphatic polyisocyanates having 4 C to 18 C in one embodiment, and6 C to 15 C in another embodiment, in the cycloalkylene residue.Cycloaliphatic diisocyanates refer to both cyclically and aliphaticallybound NCO groups, such as isophorone diisocyanate anddiisocyanatodicyclohexylmethane (H₁₂MDI).

Examples of suitable aliphatic polyisocyanates and cycloaliphaticpolyisocyanates useful in the present invention include, but are notlimited to, cyclohexane diisocyanate, methylcyclohexane diisocyanate,ethylcyclohexane diisocyanate, propylcyclohexane diisocyanate,methyldiethylcyclohexane diisocyanate, propane diisocyanate, butanediisocyanate, pentane diisocyanate, hexane diisocyanate, heptanediisocyanate, octane diisocyanate, nonane diisocyanate, nonanetriisocyanate, such as 4-isocyanatomethyl-1,8-octane diisocyanate (TIN),decane di- and triisocyanate, undecane di- and triisocyanate anddodecane di- and triisocyanate, hexamethylene diisocyanate (HDI),diisocyanatodicyclohexylmethane (H₁₂MDI), 2-methylpentane diisocyanate(MPDI), 2,2,4-trimethylhexamethylenediisocyanate/2,4,4-trimethylhexamethylene diisocyanate (TMDI),norbornane diisocyanate (NBDI), xylylene diisocyanate (XDI), 1,4- or1,3-bis(isocyanatomethyl)cyclohexane (H₆XDI), tetramethylxylylenediisocyanate, and dimers, trimers, derivatives and mixtures of the oftwo or more thereof. Suitable aliphatic polyisocyanates andcycloaliphatic polyisocyanates useful in the present invention alsoinclude, for example, XDI-based polyisocyanate, HXDI-basedpolyisocyanate, XDI isocyanurate, HDI-based polyisocyanate, H₁₂MDI-basedpolyisocyanate, HDI isocyanurate, and mixtures of two or more thereof.

In one preferred embodiment, the aliphatic-based component useful in thepresent invention includes, for example, XDI based polyisocyanate,HDI-based polyisocyanate and mixtures thereof.

Exemplary of some of the commercial products of aliphatic-basedcomponent useful in the present invention include, for example, TAKENATED-110N and TAKENATE D-120N, available from Mitsui Chemical; Desmodur N3200 and Desmodur Quix 175, available from The Coverstro Company; andmixtures thereof.

Additional isocyanate-containing compounds suitable for use according tothe present disclosure include, but are not limited to,4-methyl-cyclohexane 1,3-diisocyanate, 2-butyl-2-ethylpentamethylenediisocyanate, 3(4)-isocyanatomethyl-1-methylcyclohexyl isocyanate,2-isocyanatopropylcyclohexyl isocyanate, 2,4′-methylenebis(cyclohexyl)diisocyanate, 1,4-diisocyanato-4-methyl-pentane, and mixtures of two ormore thereof.

Also, isocyanate-containing compounds suitable for use as Component Aaccording to the present disclosure include, for example, isocyanateprepolymers. “Isocyanate prepolymers” are reaction products of apolyisocyanate and an isocyanate reactive component at a stoichiometryratio (NCO/OH) greater than (>) 2.0 in one embodiment, from 3.0 to 10.0in another embodiment, and from 4.0 to 7.0 in still another embodiment.The polyisocyanate is selected, for example, from aromaticpolyisocyanates, aliphatic polyisocyanates, cycloaliphaticpolyisocyanates, and mixtures thereof, as described above. Suitableisocyanate reactive components that can react with the polyisocyanatesto form the isocyanate prepolymers, also known as “polyurethaneprepolymers” include, for example, compounds with hydroxyl groups, aminogroups, and thio groups. The isocyanate reactive components that canreact with the polyisocyanates to form the isocyanate prepolymers usefulin the present invention include, for example, a polyether polyol, apolyester polyol, a polycaprolactone polyol, a polyacrylate, apolycarbonate polyol, a natural oil-based polyol, and mixtures of two ormore thereof.

The isocyanate reactive component that can react with thepolyisocyanates to form the isocyanate prepolymers useful in the presentinvention can also be characterized by the isocyanate reactivecomponent's hydroxyl number and its hydroxyl group functionality.“Hydroxyl number” or “hydroxyl value” is a measure of the content offree hydroxyl groups in a chemical substance. The hydroxyl number is thenumber of milligrams of potassium hydroxide (KOH) required to neutralizethe acetic acid taken up on acetylation of one gram of a chemicalsubstance that contains free hydroxyl groups. Hydroxyl number is usuallyexpressed as milligrams of potassium hydroxide per gram (mg KOH/g) ofthe chemical substance. The hydroxyl number is determined in accordancewith DIN 53240.

“Hydroxyl group functionality” is the number of hydroxyl groups presentin one molecule of a compound. Hydroxyl group functionality is measuredin accordance with ASTM D4274-16 with results reported as an integer offrom 1 or more in one embodiment and from 1 to 6 in another embodiment.

In some embodiments, the average hydroxyl number for the isocyanatereactive component can be, for example, from 1 mg KOH/g to 2,000 mgKOH/g in one embodiment, 5 mg KOH/g to 2,000 mg KOH/g in anotherembodiment, from 14 mg KOH/g to 850 mg KOH/g in still anotherembodiment, from 28 mg KOH/g to 500 mg KOH/g in yet another embodiment,and from 35 mg KOH/g to 450 KOH/g in even still another embodiment. Insome embodiments, the average molar mass of the isocyanate reactivecomponent is, for example, from 62 g/mol to 20,000 g/mol in oneembodiment, from 250 g/mol to 12,000 g/mol in another embodiment, from500 g/mol to 6,000 g/mol in still another embodiment, and from 800 g/molto 3,000 g/mol in yet another embodiment.

In some embodiments, the average hydroxyl group functionality of theisocyanate reactive component can be, for example, from 1.0 to 6.0 inone embodiment, from 1.8 to 4.0 in another embodiment, and from 2.0 to3.0 in still another embodiment. One of the advantageous propertiesexhibited by the aliphatic-based component of the present inventionincludes, for example, providing an adhesive which can be compliant withbroad governmental regulations.

Compounds having isocyanate groups are also characterized by a weightpercentage of isocyanate groups based on a total weight of the compound.The weight percentage of isocyanate groups is termed “% NCO” and ismeasured in accordance with ASTM D2572-97.

The amount of the aliphatic-based component, Component A, used in thepresent invention process is, for example, from 30 wt % to 100 wt % inone embodiment, from 40 wt % to 90 wt % in another embodiment and from50 wt % to 80 wt % in still another embodiment.

In the preferred embodiment wherein the at least one isocyanatecompound, Component A, is a blend of (i) at least one aliphatic-basedisocyanate and (ii) at least one aromatic-based isocyanate; thealiphatic-based isocyanate can any one or more of the aliphatic-basedisocyanates described above.

The aromatic-based isocyanate component, component (ii) of the aboveblend, useful in the present invention can include, for example, one ormore polyisocyanate compounds including, but are not limited to, forexample 1,3- and 1,4-phenylene diisocyanate; 1,5-naphthylenediisocyanate; 2,6-tolulene diisocyanate (2,6-TDI); 2,4-tolulenediisocyanate (2,4-TDI); 2,4′-diphenylmethane diisocyanate (2,4′-MDI);4,4′-diphenylmethane diisocyanate (4,4′-MDI);3,3′-dimethyl-4,4′-biphenyldiisocyanate (TODI) and isomers thereof;polymeric isocyanates; and mixtures of two or more thereof.

Exemplary of some of the commercial aromatic-based components useful inthe present invention can include, for example, Isonate 125 M, ADCOTTEL76-204, Coreactant CT, and Catalyst F, available from The Dow ChemicalCompany; Desmodur® E 2200/76, available from The Covestro Company; andmixtures thereof. One of the advantageous properties exhibited by thearomatic-based component of the present invention includes, for example,providing an adhesive which can be fast curing.

The amount of the aromatic-based isocyanate component, component (ii) ofComponent A (the above blend), used in the present invention process is,for example, from 5 wt % to 95 wt % in one embodiment, from 20 wt % to90 wt % in another embodiment and from 30 wt % to 90 wt % in stillanother embodiment.

As aforementioned, the at least one NCO reactive component, Component B,used to make the adhesive is; for example, at least one NCO reactivecomponent that contains (i) at least one phosphate ester compound and(ii) at least one polyol comprising a polyester polyol having an averageMw of ≥3,000 g/mol. As used herein, a “polyol” refers to a compoundhaving two or more hydroxy groups (i.e., —OH) per molecule. As usedherein, an “ester” refers to a compound that contains an ester linkage.As used herein, a “polyester” refers to a compound that contains two ormore ester linkages per molecule. A compound that is both a polyesterand a polyol is referred to herein as a “polyester polyol.” An“aliphatic polyester polyol” is a polyester polyol that contains noaromatic ring in its molecule. An “aromatic polyester polyol” is apolyester polyol that contains one or more aromatic rings in itsmolecule.

In one embodiment, the phosphate ester compound, component (i) ofComponent B, useful in the present invention can be selected, forexample, from a phosphate ester compound having the following chemicalStructure (I):

where R¹ is any organic group. In addition to the pendant groups shownin Structure (I), R¹ may or may not have one or more additional pendant—OH groups, and R¹ may or may not have one or more additional pendantgroups of Structure (I). Any two or more of the —OH groups and thegroup(s) of Structure (I) may or may not be attached to the same atom ofR¹. In a preferred embodiment, each —OH group and each group ofStructure (I) is attached to a separate atom of R¹.

A convenient way to characterize R¹ is to describe the compound havingthe following Structure (II):

where R¹ is the same as in Structure (I). The compound having Structure(II) is referred to herein as a “precursor polyol.”

In some embodiments, suitable precursor polyols have number average Mwof 90 g/mol or higher in one embodiment, 200 g/mol or higher in anotherembodiment, and 400 g/mol or higher in still another embodiment. In someembodiments, suitable precursor polyols have number average Mw of 4,000g/mol or lower in one embodiment, 2,000 g/mol or lower in anotherembodiment, 1,200 g/mol or lower in still another embodiment, 900 g/molor lower in yet another embodiment, and 500 g/mol or lower in even stillanother embodiment. In some embodiments, suitable precursor polyols havenumber average Mw of from 200 g/mol to 4,000 g/mol in one embodiment,from 400 g/mol to 2,000 g/mol in another embodiment, from 400 g/mol to1,200 g/mol in still another embodiment, and from 400 g/mol to 900 g/molin yet another embodiment.

In some embodiments, suitable precursor polyols are alkyl higherpolyols, monosaccharides, disaccharides, and compounds having Structure(III):

where each of R², R³, R⁴, and R⁵ is, independent of the other, anyorganic group; each of n₁, n₂, and n₃ is, independent of the other, aninteger from 0 to 10. In addition to the pendant groups shown inStructure (III), R² may or may not have one or more additional pendantgroups. It is further understood that any two or more of the pendantgroups may or may not be attached to the same atom of R². In someembodiments, a mixture of compounds having Structure (III) is present,where the compounds of Structure (III) differ from each other in thevalue of one or more of n₁, n₂, and n₃. Such mixtures are describedherein by stating a non-integer value for the parameter n₁, n₂, or n₃,where the non-integer value represents the number average of thatparameter. When it is desired to assess the molecular weight of such amixture, the number-average molecular weight is used.

Among precursor polyols having Structure (III), in one preferredembodiment each pendant group is attached to a separate atom of R².Among precursor polyols having Structure (III), in another preferredembodiment, one or more of R³, R⁴, and R⁵ is a hydrocarbon group having1 C to 4 C in one embodiment, 2 C to 3 C in another embodiment, and 3 Cin still another embodiment. Among precursor polyols having Structure(III), in still another preferred embodiment, one or more of R³, R⁴, andR⁵ is an alkyl group, which may be linear or cyclic or branched or acombination thereof; in yet another preferred embodiment, one or more ofR³, R⁴, and R⁵ is a linear or branched alkyl group; and in even stillanother preferred embodiment, one or more of R³, R⁴, and R⁵ is abranched alkyl group. In even yet another preferred embodiment, R³, R⁴,and R⁵ are identical to each other.

Among precursor polyols having Structure (III), in one preferredembodiment, one or more of n₁, n₂, and n₃ is from 0 to 8. Amongprecursor polyols having Structure (III), in another preferredembodiment, one or more of n₁, n₂, and n₃ is 1 or more. Among precursorpolyols having Structure (III), in still another preferred embodiment,one or more of n₁, n₂, and n₃ is 6 or less. Among precursor polyolshaving Structure (III), in yet another preferred embodiment, n₁, n₂, andn₃ are the same as each other.

In one embodiment, the group of precursor polyols having Structure (III)are compounds in which each of R², R³, R⁴, and R⁵ is an alkyl group;such precursor polyols are known herein as alkoxylated alkyl triols. Ina triol, when at least one of n₁, n₂, and n₃ is 1 or more and R² has thefollowing Structure (IV):

then the triol is known herein as an alkoxylated glycerol. Inalkoxylated triols, when each of R³, R⁴, and R⁵ is a branched alkylgroup with exactly 3 C, the alkoxylated triol is known herein as apropoxylated triol. A propoxylated triol in which R² has Structure (IV)is known herein as propoxylated glycerol.

Among precursor polyols that are alkyl higher polyols, in one embodimentare compounds with 10 C or fewer carbon atoms; in another embodiment arecompounds with 6 C or fewer carbon atoms; in still another embodimentare compounds with 3 or fewer carbon atoms; and in yet anotherembodiment the compound is glycerol.

In even still another embodiment, precursor polyols are alkyl higherpolyols and compounds having Structure (III). It is noted that, if n₁ isequal to (=) n₂=n₃=0 and if R² is either an alkyl group or an alkylgroup having hydroxyl groups, then the compound having Structure (IV) isan alkyl higher polyol.

In one embodiment, the group of precursor polyols are alkyl triols andalkoxylated alkyl triols. Among these compounds, are glycerol andalkoxylated glycerols in one embodiment; and alkoxylated glycerols inanother embodiment. Among alkoxylated glycerols, are propoxylatedglycerols in one preferred embodiment.

Another class of suitable phosphate ester compound useful in the presentinvention includes compounds that contain urethane linkages. Phosphateester compounds containing urethane linkages are made by reacting one ormore suitable phosphate-functional polyol with one or morepolyisocyanate, and in a preferred embodiment including one or morediisocyanate. In a preferred embodiment, the amount of polyisocyanate iskept low enough so that some or all of the reaction products arephosphate-functional polyols. Alternatively, the polyol may be firstreacted with the polyisocyanate to make an —OH terminated prepolymerwhich is then reacted with polyphosphoric acid. The phosphate estercompound with urethane linkages include those compounds having a numberaverage Mw in the range of 1,000 g/mol to 6,000 g/mol in one generalembodiment, in the range of 1,200 g/mol to 4,000 g/mol in anotherembodiment, and in the range of 1,400 g/mol to 3,000 g/mol in stillanother embodiment.

In some embodiments, the phosphate ester compound is the reactionproduct of reactants including a precursor polyol and a phosphoric-typeacid, and the resulting phosphate ester compound has the chemicalstructure of Structure (I).

In one preferred embodiment, the amounts of phosphoric-type acid andprecursor polyol are chosen to determine the ratio of M_(p):M_(x) asfollows: M_(hy)=the number of hydroxyl groups per molecule of theprecursor polyol; N_(x)=M_(hy)−2; M_(x)=(the moles of precursorpolyol)×(N_(x)); and M_(p)=the moles of phosphorous atoms contained inthe phosphoric-type acid.

In general, the ratio of M_(p):M_(x) is 0.1:1 or higher in oneembodiment, 0.2:1 or higher in another embodiment, 0.5:1 or higher instill another embodiment, and 0.75:1 or higher in yet anotherembodiment. In some embodiments, the ratio of M_(p):M_(x) is 1.1:1 orlower.

Generally, the weight ratio of phosphoric-type acid to precursor polyolis 0.005:1 or higher in one embodiment, 0.01:1 or higher in anotherembodiment, and 0.02:1 or higher in still another embodiment. In someembodiments, the weight ratio of phosphoric-type acid to precursorpolyol is 0.3:1 or lower, or 0.2:1 or lower, or 0.12:1 or lower.

In some embodiments, the phosphoric-type acid contains polyphosphoricacid. And, in general, the amount of polyphosphoric acid in thephosphoric-type acid is, by weight based on the weight of thephosphoric-type acid, 75 wt % or more in one embodiment, 80 wt % or morein another embodiment, and 90 wt % or more in still another embodiment.Polyphosphoric acid is available in various grades; each grade ischaracterized by a percentage. To determine the grade, it is firstrecognized that pure monomeric orthophosphoric acid, the content ofphosphorous pentoxide is considered to be 72.4%. Any grade ofpolyphosphoric acid can also be analyzed, to consider that one mole ofpolyphosphoric acid (formula weight labeled “Fppa”) contains the numberof moles of phosphorous pentoxide labeled “Nppo,” and the phosphorouspentoxide percentage (“PCppo”) is given by PCppo=(Nppo X 142)/Fppa,expressed as a percentage. Then, the grade of that polyphosphoric acidis the ratio, expressed as a percentage: Grade=PCppo/72.4.

In some embodiments, the polyphosphoric acid used has grade of 100% orhigher in one embodiment, and 110% or higher in another embodiment. Insome embodiments, the polyphosphoric acid used has grade of 150% orlower in one embodiment, and 125% or lower in another embodiment.

In some embodiments, the disclosed solvent-based adhesive compositionscontain one or more phosphorous-free polyols in addition to the one ormore phosphate-functional polyols.

Further information about suitable phosphate esters and the preparationof such suitable phosphate esters can be found, for example, in PCTPublication No. WO/2015/168670.

Generally, the amount of the phosphate ester compound, component (i) ofComponent B, used in the present invention is from 0.1 wt % to 80 wt %in one embodiment, from 1 wt % to 70 wt % in another embodiment, from 5wt % to 60 wt % in still another embodiment; from 10 wt % to 60 wt % inyet another embodiment, and from 20 wt % to 60 wt % in even stillanother embodiment, based on the dry weight of the polyol component,Component B.

The polyol component, component (ii) of Component B, useful in thepresent invention comprises at least one polyester polyol. Generally,the polyester polyol has a molecular weight of ≥3,000 g/mol in oneembodiment, ≥3,500 g/mol in another embodiment, and from 3,000 g/mol to20,000 g/mol in still another embodiment.

Suitable polyester polyols useful in the present invention include, butare not limited to, for example, aliphatic polyester polyols, aromaticpolyester polyols, copolymers of aliphatic and aromatic polyesterpolyols, polycarbonate polyols, and polycaprolactone polyols; andmixtures thereof. These polyester polyols: are the reaction products ofpolybasic acids and polyhydric alcohols; or are the reaction of phosgeneor a carbonate monomer with a polyhydric alcohol; or are produced viaring opening polymerization of cyclic ester compounds.

Exemplary of suitable polybasic acids useful in the present inventioninclude succinic acid, adipic acid, azelaic acid, sebacic acid,dodecanedicarboxylic acid, maleic anhydride, fumaric acid,1,3-cyclopentane-dicarboxylic acid, 1,4-cyclohexanedicarboxylic acid,terephthalic acid, isophthalic acid, phthalic acid,1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid,2,6-naphthalenedicarboxylic acid, naphthalic acid, biphenyldicarboxylicacid, 1,2-bis(phenoxy)ethane-p,p′-dicarboxylic acid, and anhydrides orester-forming derivatives of these dicarboxylic acids; andp-hydroxybenzoic acid, p-(2-hydroxyethoxy)benzoic acid, andester-forming derivatives or dimer acids of these dihydroxycarboxylicacids; and mixtures thereof. These polybasic acids may be used alone orin a combination of two or more polybasic acids.

Any known polyhydric alcohol can be used according to this disclosure.Non-limiting examples of suitable polyhydric alcohols useful in thepresent invention include: glycols such as ethylene glycol, propyleneglycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol,3-methyl-1,5-pentanediol, 1,6-hexanediol, neopentylglycol,methylpentanediol, dimethylbutanediol, butylethylpropanediol, diethyleneglycol, triethylene glycol, tetraethylene glycol, dipropylene glycol,tripropylene glycol, bishydroxyethoxybenzene, 1,4-cyclohexanediol,1,4-cyclohexane-dimethanol, triethylene glycol, polycaprolactone diol,dimer diol, bisphenol A, and hydrogenated bisphenol A; polyestersproduced through ring opening polymerization of cyclic ester compoundssuch as propiolactone, butyrolactone, ε-caprolactone, 8-valerolactone,and β-methyl-δ-valerolactone; and polyesters produced from additionpolymerization of one or more monomers including ethylene oxide,propylene oxide, butylene oxide, styrene oxide, epichlorohydrin,tetrahydrofuran, and cyclohexylene in the usual manner with the aid ofone or more compounds containing two active hydrogen atoms as aninitiator, e.g., ethylene glycol, diethylene glycol, triethylene glycol,propylene glycol, trimethylene glycol, 1,3-butanediol, 1,4-butanediol,1,6-hexanediol, and neopentyl glycol; and mixtures thereof. Thesepolyhydric alcohols may be used alone or in a combination of two or morepolyhydric alcohols.

Generally, the amount of the polyester polyol, component (ii) ofComponent B, used in the present invention is from 20 wt % to 99.9 wt %in one embodiment, from 30 wt % to 99 wt % in another embodiment, from40 wt % to 95 wt % in still another embodiment; from 40 wt % to 90 wt %in yet another embodiment, and from 40 wt % to 80 wt % in even stillanother embodiment, based on the dry weight of the polyol component,Component B.

In addition to the polyester polyol component, component (ii) ofComponent B, the polyol Component B can optionally include (iii) atleast one polyether polyol. Generally, the polyether polyol has amolecular weight of less than 1,500 g/mol in one embodiment, less than1,000 g/mol in another embodiment, and from 50 g/mol to 1,500 g/mol instill another embodiment. In another embodiment, polyether polyolshaving a molecular weight of from 150 g/mol to 1,500 g/mol and afunctionality of from 2.0 to 6.0 can be incorporated in the polyolcomponent, Component B

Exemplary of suitable polyether polyols useful in the present inventioninclude, but are not limited to, for example, polypropylene glycols,polytetramethylene ether glycols, polybutylene oxide-based polyols, andcopolymers thereof; and mixtures thereof.

Exemplary of suitable polypropylene glycols useful in the presentinvention include, but are not limited to, for example, polyols based onpropylene oxide, ethylene oxide, or mixture of them with initiatorsselected from propylene glycol, dipropylene glycol, sorbitol, sucrose,glycerin, and/or mixtures thereof. For example, the polypropyleneglycols can include VORANOL™, available from The Dow Chemical Company;PLURACOL™, available from the BASF Company; POLY-G™, POLY-L™, andPOLY-Q™, available from Lonza; and ACCLAIM™ available from Covestro; andmixtures thereof.

Exemplary of suitable polytetramethylene ether glycols useful in thepresent invention include, but are not limited to, for example, POLYTHF™available from the BASF Company; TERTHANE™ available from Invista; PTMG™available from Mitsubishi; and PTG™ available from Dairen; and mixturesthereof.

Exemplary of suitable polybutylene oxide-based polyols useful in thepresent invention include, but are not limited to, for example,polybutylene oxide homopolymer polyols, polybutylene oxide-polypropyleneoxide copolymer polyols, and polybutylene oxide-polyethylene oxidecopolymer polyols; and mixtures thereof.

In other embodiments, the polyether polyols useful in the presentinvention, include, but are not limited to, for example, low molecularweight glycols, including, but not limited to, for example, ethyleneglycol, diethylene glycol, triethylene glycol, propylene glycol,trimethylene glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol,trimethylolpropane, triisopropanolamine, neopentyl glycol; and mixturesthereof.

The amount of the polyether polyol optional component (iii) of ComponentB, which can be added to the polyol component, Component B, when used,can include, for example, from 0 wt % up to 20 wt % in one embodiment,from 0.01 wt % to 15 wt % in another embodiment, and from 0.1 wt % to 10wt % in still another embodiment, based on the dry weight of the polyolcomponent, Component B.

In general, the adhesive composition of the present invention includes(C) at least one solvent, as Component C. For example, but are notlimited to, the solvent can be selected from the group consisting ofethyl acetate, methyl ether ketone, toluene, and mixture thereof.

The amount of the solvent, Component C, used in the present inventionprocess can be, for example, from 20 wt % to 90 wt % in one embodiment,from 30 wt % to 80 wt % in another embodiment and from 40 wt % to 70 wt% in still another embodiment, based on the total amount of thecomponents in the adhesive composition.

In some embodiments, the adhesive composition of the present inventioncan include (D) one or more additional optional conventional ingredientsor additives, as Component D, including but are not limited to, forexample, catalysts, tackifiers, plasticizers, rheology modifiers,adhesion promoters, antioxidants, fillers, colorants, pigments,surfactants, solvents, polymers (including, for example, thermoplasticresins other than those discussed herein above), dehydrating agents(including, for example, silanes), benzoyl chloride, other polyols(including, for example, fatty polyols), ultraviolet indicators, andcombinations of two or more thereof.

As an illustrative embodiment, the adhesive composition may include, forexample, an adhesion promoter. Non-limiting examples of suitableadhesion promoters include coupling agents such as a silane couplingagent, a titanate coupling agent, and an aluminate coupling agent; epoxyresin, phosphoric acid, polyphosporic acid, and phosphate esters.

Examples of the silane coupling agent useful in the present inventioninclude, but are not limited to, aminosilanes such asγ-aminopropyltriethoxysilane, γ-aminopropyl-trimethoxysilane,N-β(aminoethyl)-γ-aminopropyltrimethoxysilane,N-β(aminoethyl)-γ-aminopropyltrimethyl dimethoxysilane, andN-phenyl-γ-aminopropyltrimethoxysilane; epoxysilanes such asβ-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane,γ-glycidoxypropyl-trimethoxysilane, andγ-glycidoxypropyltriethoxysilane; vinylsilanes such as vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane,vinyltrimethoxysilane, and γ-methacryloxypropyltrimethoxysilane;hexamethyldisilazane; γ-mercaptopropyl-trimethoxysilane; and mixturesthereof.

Examples of the titanate coupling agent useful in the present inventioninclude, but are not limited to, tetraisopropoxy titanium,tetra-n-butoxy titanium, butyl titanate dimer, tetrastearyl titanate,titanium acetylacetonate, titanium lactate, tetraoctyleneglycoltitanate, titanium lactate, tetra stearoxy titanium; and mixturesthereof.

Examples of the epoxy resin useful in the present invention include, butare not limited to, a variety of readily available epoxy resins such asbisphenol A-epichlorohydrin (epi-bis) type epoxy resin, novolak typeepoxy resin, β-methylepichlorohydrin type epoxy resin, cyclic oxiranetype epoxy resin, glycidyl ether type epoxy resin, glycidyl ester typeepoxy resin, polyglycol ether type epoxy resin, glycol ether type epoxyresin, epoxidation fatty acid ester type epoxy resin, polycarboxylicacid ester type epoxy resin, aminoglycidyl type epoxy resin, resorcintype epoxy resin; and mixtures thereof.

In some embodiments, the adhesion promoter can be a phosphate estercompound. In other embodiments, the adhesion promoter is an epoxy silane((3-glycidyloxypropyl)-trimethoxysilane). In some embodiments,phosphoric acid can be incorporated in the polyol component while epoxysilane can be incorporated in the isocyanate component. In someembodiments, both epoxy silane and phosphoric are incorporated in thepolyol component.

In some embodiments, the average functionality of the adhesivecomposition (i.e., the isocyanate component together with the polyolcomponent), excluding non-reactive components such as solvents, is from2 to 2.5.

The amount of the optional components, Component D, when used can be,for example, from 0 wt % to 15 wt % in one embodiment, from 0.01 wt % to10 wt % in another embodiment and from 0.1 wt % to 5 wt % in stillanother embodiment.

In one broad embodiment, the process of producing the adhesivecomposition includes mixing the isocyanate and polyol componentsdescribed above to form a curable adhesive composition. It iscontemplated that two parts, an isocyanate part and a polyol componentpart, is employed in the present invention. It is also contemplated thatthe isocyanate component and the polyol component of the disclosedadhesive composition can be made separately and, if desired, storeduntil it is desired to use the adhesive composition. In someembodiments, both the isocyanate component and the polyol component areeach liquid at 25° C. When it is desired to use the adhesivecomposition, the isocyanate component and the polyol component arebrought into contact with each other and mixed together, typically at astoichiometric ration (NCO/OH) between 1 and 2.5. It is contemplatedthat when these two components are brought into contact, a curingreaction begins in which the isocyanate groups react with the hydroxylgroups to form urethane links. The adhesive composition formed bybringing the two components into contact can be referred to as a“curable mixture.”

To form the adhesive composition, mixing of the two components may takeplace at any suitable time in the process of forming the adhesivecomposition and applying the adhesive to a substrate, such as before,during, or as a result of the application process. All of the presentsteps may be carried out under ambient room temperature conditions. Asdesired, heating or cooling may be employed. And, the mixing can becarried out using a suitable conventional mixer, such as using anelectrically, pneumatically, or an otherwise powered mechanical mixer.

In a general embodiment, the process for preparing the solvent-basedadhesive composition of the present invention includes, for example, thesteps of (1) providing the isocyanate component; (2) providing thepolyol component; (3) mixing the two components to form a resin mixture;(4) diluting the resin mixture in a solvent to form a diluted resinmixture having an application solid content of from 25 wt % to 55 wt %in one embodiment, from 30 wt % to 45 wt % in another embodiment, andfrom 35 wt % to 40 wt % in still another embodiment, based on the totalweight of the diluted resin mixture; and (5) removing the solvent fromthe composition to form the adhesive composition before the compositionis applied to a substrate and before the composition is cured.

Before the resin mixture is cured the mix ratio of the isocyanatecomponent to the polyol component is from 100:1 to 100:12 in oneembodiment, and from 100:4 to 100:10 in another embodiment.

Some of the advantageous properties exhibited by the solvent-basedadhesive composition of the present invention includes, for example, (1)good adhesion performance; (2) fast curing; and (3) either (a) no levelof migrated undesirable aromatic amines such as MDA and TDA, or (b) alow level of migrated undesirable aromatic amines such as MDA and TDAinto food packed in packages using the adhesive.

For example, the dry bond of the adhesive before retort testing can begreater than 500 g/25 mm in one embodiment, from 500 g/25 mm to 2,500g/25 mm in another embodiment, from 700 g/25 mm to 2000 g/25 mm in stillanother embodiment and from 800 g/25 mm to 1,800 g/25 mm in yet anotherembodiment.

For example, the bond of the adhesive after 1 hr of retort testing at121° C. can be greater than 200 g/25 mm in one embodiment, from 200 g/25mm to 2,500 g/25 mm in another embodiment and from 300 g/25 mm to 2,000g/25 mm in still another embodiment. The bond can be dependent on thetype of film substrate used and in some embodiments the films can bebonded where after testing the substrates failure mode occurs before thebond.

The curing time of the adhesive can be from 1 day to 8 days in oneembodiment, from 1 day to 7 days in another embodiment and from 2 daysto 7 days in still another embodiment.

A process of forming a laminate using the adhesive composition of thepresent invention is also disclosed herein. In some embodiments, theadhesive composition, such as the adhesive composition discussed above,is in a liquid state at 25° C. Even if the composition is solid at 25°C., it is acceptable to heat the composition as necessary to transformthe composition into a liquid state. Solvent is added to the mixedadhesive composition until the desired solids content is reached. Ingeneral, a solids content of 50% or greater is used in one embodiment.

The adhesive composition of the present invention is useful for bondingsubstrates together; and the adhesive composition can be used on a widevariety of a single suitable substrate or a plurality of suitablesubstrates. The substrates may be similar materials or dissimilarmaterials. For example, in some embodiments, the substrate may beselected from high, low or medium density plastics (e.g., of a typeselected from polystyrene, polyethylene, ABS, polyurethane, polyethyleneterephthalate, polybutylene terephthalate, polypropylene, polyphenylene,polycarbonate, polyacrylate, polyvinyl chloride, polysulfone, andmixtures thereof), paper, wood and reconstituted wood products, polymercoated substrates, wax coated paperboard, cardboard, particle board,textiles, leather, and metal (e.g., aluminum, ferrous as well as othernon-ferrous), metallized plastics (e.g., metallized plastic film) or thelike.

Wet and dry bond lamination of a plurality of substrate layers ispossible. The adhesive composition can be applied to desired substratesusing conventional application techniques such as rotogravure printing,flexographic printing, conventional or airless spray, roll coating,brush coating, wire wound rod coating, knife coating, or coatingprocesses such as curtain-, flood-, bell-, disc-, and dip-coatingprocesses. Coating a substrate with the adhesive composition may be doneover the entire surface of the substrate or to a portion of thesubstrate's surface, such as along an edge, or at intermittentlocations. Once applied to the substrate, the adhesive composition isdried, such as by application of heat and air flow, or some othersuitable conventional approach for removing substantially all remainingsolvent present in the adhesive composition.

A laminate comprising the solvent-based adhesive composition of thepresent invention can be formed by applying the adhesive to at least oneof two separate substrates and combining the substrates together suchthat the adhesive is disposed between the surfaces of the twosubstrates; and then curing the adhesive to form a bond between the twosubstrates. The substrates can include, for example, two separate films;and each of the films can be made of a different material or of the samematerial. Generally, a layer of the adhesive composition is applied to asurface of a film. In one embodiment, the thickness of the layer of thecurable adhesive composition mixture applied to a surface of a film isfrom 1 micron (μm) to 5 μm. As used herein, a “film” is any structurethat is 0.5 mm or less in one dimension of the structure; and is 1centimeter (cm) or more in both of the other two dimensions of thestructure.

In some embodiments, a surface of another film is brought into contactwith the layer of the curable mixture to form an uncured laminate. Thecurable mixture is then cured or allowed to cure. The uncured laminatemay be subjected to pressure, for example by passing through niprollers, which may or may not be heated. The uncured laminate may beheated to speed the cure reaction.

Suitable substrates used to form the laminate structure include filmssuch as paper, woven and nonwoven fabric, polymer films, metal foil,metal-coated (metallized) polymer films, and combinations thereof. Thesubstrates are layered to form a laminate structure, with an adhesivecomposition according to the present invention adhering one or more ofthe substrates together. Films can optionally have a surface on which animage is printed with ink. The ink may be in contact with the adhesivecomposition. In some embodiments, the films are polymer films andmetal-coated polymer films, and in a preferred embodiment the films arepolymer films. A “polymer film” is a film that is made of a polymer ormixture of polymers. The composition of a polymer film is, typically, 80wt % or more of one or more polymers.

The adhesive composition is particularly attractive for packaging andsealing applications. For example, a plastic film, metal film, ormetallized plastic film can be laminated (e.g., over all of its surfaceor at least a portion of its surface, such as along its edges, or atintermittent locations) with the adhesive composition of the presentinvention to form a laminate. In one preferred embodiment, the laminateis used, for example, to form a pouch made of at least two layers offilm with the adhesive bonded inbetween the two film layers. In someembodiments, food may be packaged for boil-in-bag preparation, or theresulting laminate might be used for sealing or packaging some otherarticle.

EXAMPLES

The following examples are presented to further illustrate the presentinvention in detail but are not to be construed as limiting the scope ofthe claims. Unless stated to the contrary, implicit from the context, orcustomary in the art, all parts and percentages are based on weight andall test methods are current as of the filing date of this disclosure.

Various raw materials or ingredients used in the Inventive Examples(Inv. Ex.) and the Comparative Examples (Comp. Ex.) are explained inTable I as follows:

TABLE I Raw Materials Ingredient Brief Description Supplier ISONATE ™125M pure solid MDI The Dow Chemical Company (Dow) ADCOTE ™ 545Epolyester polyol with an OHN of about 8.5 KOH/mg Dow VORANOL ™ CP 450polyether polyol with a molecular weight of about Dow 450 g/mol (triol)Polyphosphoric acid 115% polyphosphoric acid Sigma Aldrich Co-reactantCT polyether-rich isocyanate-terminated compound Dow based on MDIisocyanate MOR-FREE ™ C33 HDI-based aliphatic isocyanate with 100%solids Dow ADCOTE ™ 811AEA polyurethane polyester polyol Dow TAKENATE ™D-110 N XDI-based aliphatic isocyanate with a solid The Mitsui Chemicalconcentration of 75 wt % Company 9L10 IPDI-based aliphatic isocyanatewith a solid Dow concentration of 75 wt % ethyl acetate urethane gradesolvent used for adhesive Fisher Scientific formulations

Examples 1 to 4 and Comparative Examples A to C—Adhesives

The ingredients of the adhesive formulations used in the Examples aredescribed in Table II; and the adhesive formulations are prepared inaccordance with the following procedures:

General Procedure for Preparing the Phosphate Ester Compound

A 1 liter (L) multi-neck round bottom flask was dried in an oven,flushed with dry nitrogen (N₂) for 30 min, then charged with 150 grams(g) of VORANOL™ CP 450 polyether polyol and placed under an N₂ sweep of70 milliliters per minute (mL/min). A syringe was loaded with 4 g of115% Polyphosphoric 20 acid (PPA). The PPA was added dropwise to thepolyether polyol with strong agitation. A minimal temperature increasewas observed. The reactor contents were heated to 100° C. for 1 hr thencooled to 45° C. Then, 40 g of ethyl acetate was added to the reactor,followed by a slow addition of 50 g of ISONATE™ 125M diisocyanate. Asignificant exotherm was controlled with the application of an ice batchto keep the reaction pot below 75° C. and development of a yellow 25 toamber color was observed. The reactor was then maintained at 65° C. for1 hr, at which point the content was cooled and packaged. The producthad the following properties: 76.0% solids, a hydroxyl number (OHN) of112 mg KOH/g, acid value (AV) of 19.0 mg KOH/g, and a viscosity at 25°C. of 1,665 millipascals-seconds (mPa·s).

General Procedure for Preparing the Isocyanate Component (Component A)

The pertinent ingredients for preparing the isocyanate-reactivecomponents of Inventive Example 1 and Inventive Example 2 are describedin Table II. Using the isocyanate component of Inventive Example 1 as atypical example for sample preparation, about 450 g of ADCOTE™ 577 andabout 50 g of MOR-FREE™ C33 are charged into a glass reactor. Thereactor is heated to about 40° C. and the resulting mixture is stirredfor about 30 min at 40° C. Then, the resulting sample mixture ispackaged and placed in storage for later use.

General Procedure for Preparing the Isocyanate-Reactive Component(Component B)

The pertinent ingredients for preparing the isocyanate-reactivecomponents of Inventive Example 1 and Inventive Example 2 are describedin Table II. Using the isocyanate-reactive component of Example 1 as atypical example for sample preparation, about 400 g of VORANOL™ CP450,about 40 g of POLYG™ 30-112 and about 360 g of phosphate ester compoundare charged to a glass reactor. The reactor is heated to about 40° C.and the resulting mixture is stirred for about 30 min at 40° C. Then,the resulting sample mixture is packaged and placed in storage for lateruse.

General Procedure for Preparing the Adhesive Formulation

The pertinent ingredients for preparing the adhesive formulationsincluding the isocyanate-reactive component, the isocyanate componentand solvent are described in Table II. Using the adhesive of InventiveExample 1 as a typical example for an adhesive formulation samplepreparation, about 1,000 g of isocyanate component (Component A), about160 g of isocyanate-reactive component (Component B) and about 1,460 gof ethyl acetate are loaded into a plastic container. The materials aremixed using a mechanical mixer at room temperature (about 25° C.) for 30min to obtain the formulated adhesive of Inventive Example 1.

TABLE II Adhesive Formulations Example No. of Adhesive Formulation(parts) Inv. Ex. 1 Inv. Ex.2 Inv. Ex.3 Inv. Ex.4 Comp. Ex. A Comp. Ex. BComp. Ex. C Ingredient Ad* Al Ad A2 Ad A3 Ad A4 Ad A5 Ad A6 Ad A7Component A {Isocyanate Side) Coreactant CT 4.5 6.5 8 14 MOR-FREE ™ C336 4.5 TAKENATE ™ D-110N 12 6.5 9L10 8 Component B (Polyol Side) ADCOTE ™545 E 98 98 98 98 100 98 Phosphate ester 2 2 2 2 2 compound ADCOTE ™811AEA 100 Solvent Ethyl acetate 96 100 98 100 92 92 100 *“Ad” standsfor “adhesive”.

Examples 5 to 12 and Comparative Examples D to G—Laminates GeneralProcedure for Preparing Laminates

Table III describes various films used in the Examples to prepare thelaminates and the laminate samples using the adhesives described inTable II above. The laminates based on the solvent-based adhesives wereproduced via a Nordmeccanica Labo Combi 400 pilot coater at roomtemperature (about 25° C.). Polymer films were corona treated beforelamination and an aluminum (Al) foil was used without corona treatment.The coat weight of each laminate was maintained at about 4.9 grams persquare meter (g/m²). The prepared laminates were subsequently cured in acontrolled environment (e.g., at 25° C. and 50% relative humidity at 50°C.).

The Examples are prepared using films including a “Prelam” which is a 12m (48 gauge) polyester (“PET”) film laminated to a 0.00035 mil Al foilwith ADCOTE™/Coreactant F at 3.26 g/m² (2.00 lbs/ream), commerciallyavailable from The Dow Chemical Company; and a cast polypropylene(“CPP”) film with a thickness of 3 mil (75 μm).

TABLE III Film Laminates Film Laminate Sample Example No. BriefDescription of Film Sample Substrates Layered Structure Inv. Ex. 5 Firstsubstrate is Prelam (Al foil side contacts Ad*); Foil//Adhesive A1//CPPsecond substrate is CPP; and adhesive is Ad A1. Laminate is cured at 25°C. for 7 days. Inv. Ex. 6 First substrate is Prelam (Al foil sidecontacts Ad); Foil//Adhesive A2//CPP second substrate is CPP; andadhesive is Ad A2. Laminate is cured at 25° C. for 5 days. Inv. Ex. 7First substrate is Prelam (Al foil side contacts Ad); Foil//AdhesiveA3//CPP second substrate is CPP; and adhesive is Ad A3. Laminate iscured at 25° C. for 7 days. Inv. Ex. 8 First substrate is Prelam (Alfoil side contacts Ad); Foil//Adhesive A4//CPP second substrate is CPP;and adhesive is Ad A4. Laminate is cured at 25° C. for 5 days. Inv. Ex.9 First substrate is Prelam (Al foil side contacts Ad); Foil//AdhesiveA1//CPP second substrate is CPP; and adhesive is Ad A1. Laminate iscured at 50° C. for 3 days. Inv. Ex. 10 First substrate is Prelam (Alfoil side contacts Ad); Foil//Adhesive A2//CPP second substrate is CPP;and adhesive is Ad A2. Laminate is cured at 50° C. for 3 days. Inv. Ex.11 First substrate is Prelam (Al foil side contacts Ad); Foil//AdhesiveA3//CPP second substrate is CPP; and adhesive is Ad A3. Laminate iscured at 50° C. for 3 days. Inv. Ex. 12 First substrate is Prelam (Alfoil side contacts Ad); Foil//Adhesive A4//CPP second substrate is CPP;and adhesive is Ad A4. Laminate is cured at 50° C. for 3 days. Comp. Ex.D First substrate is Prelam (Al foil side contacts Ad); Foil//AdhesiveA5//CPP second substrate is CPP; and adhesive is Ad A5. Laminate iscured at 50° C. for 10 days. Comp. Ex. E First substrate is Prelam (Alfoil side contacts Ad); Foil//Adhesive A5//CPP second substrate is CPP;and adhesive is Ad A5. Laminate is cured at 25° C. for 21 days. Comp.Ex. F First substrate is Prelam (Al foil side contacts Ad);Foil//Adhesive A6//CPP second substrate is CPP; and adhesive is Ad A6.Laminate is cured at 50° C. for 3 days. Comp. Ex. G First substrate isPrelam (Al foil side contacts Ad); Foil//Adhesive A7//CPP secondsubstrate is CPP; and adhesive is Ad A7. Laminate is cured at 50° C. for3 days. *“Ad” stands for “adhesive”.

Testing and Measurement Methods of Films Bond Strength Measurement

The 900 T-peel test was carried out on laminate samples cut to 15 mmwide and 1-inch (25.4 mm) long strips and pulled on a Thwing Albert™QC-3A peel tester equipped with a 50 Newtons (N) loading cell at a rateof 10 inch/min (254 mm/min) on the 1-inch (25.4 mm) strips. Threeseparate sample strips were tested and the results values of the threestrips were averaged. When the two films in the laminate separated(peeled), the average of the force during the pull was recorded. If oneof the films stretched or broke, the maximum force or force at break wasrecorded. The failure mode (FM) or mode of failure (MOF) was recordedaccording to the following designations:

“FS” stands for “film stretch”.

“FT” stands for “film tears” (or “breaks”).

“DL” stands for “delaminated”, which denotes that a secondary filmseparated from the primary film.

“AT” stands for “adhesive transfer”, which denotes that the adhesivefails to adhere to the primary film and is transferred to the secondaryfilm.

“AS” stands for “adhesive split” (or cohesive failure), which denotesthat adhesive is found on both primary and secondary films.

“MT” stands for “metal transfer”, which denotes that a transfer of metalfrom a metalized film to a secondary film occurred.

“PMT” stands for “partial metal transfer”.

The initial or “green” bonds were tested as soon as possible after thelaminate was made. Additional T-peel tests were conducted at the timeintervals indicated below.

Curing Time

ATR was used to monitor the curing of the inventive and comparativeadhesives in the Foil//CPP structure and the curing time for eachadhesive used was determined when isocyanate peak disappeared from theATR spectrum.

General Procedure for Preparing Pouches

Laminates were made from the Prelam//CPP as described above. One of the9 inches×12 inches (23 cm×30.5 cm) sheets of laminate was folded over togive a double layer of about 9 inches×6 inches (23 cm×15.3 cm) such thatthe CPP film of one layer was in contact with the CPP film of the otherlayer. The edges of the folded laminate were trimmed on a paper cutterto give a folded piece of about 5 inches×7 inches (12.7 cm×17.8 cm). Twolong sides and one short side of the folded piece was heat sealed at theedges to give a finished pouch with an interior size of 4 inches×6inches (10.2 cm×15.2 cm). The heat sealing was done at 400° F. (204° C.)for 1 second (s) at a hydraulic pressure of 40 pounds per square inch(psi) (276 kilopascals [kPa]). Two or three pouches were made for eachtest.

Testing and Measurement Methods of Pouches Retort Performance Testing

The pouches prepared as described above were filled through the openedge with 100 milliliters (mL)±5 mL of distilled water (DI water) or1:1:1 sauce (blend of equal parts by weight of ketchup, vinegar, andvegetable oil). Splashing the filling onto the heat seal area wasavoided as this could cause the heat seal to fail during the test. Afterfilling, the top of the pouch was sealed in a manner that minimized airentrapment inside of the pouch. The seal integrity was inspected on allfour sides of pouches to ensure that there were no flaws in the sealingthat would cause the pouch to leak during the test. Any defected poucheswere discarded and replaced. In some cases, flaws in the laminate weremarked to identify whether new additional flaws were generated duringthe testing.

The pouches, containing 1:1:1 sauce, were then placed in a STERISautoclave set at 121° C. for 1 hr. The pouches were removed after retortand the extent of tunneling, blistering, de-lamination, or leakage wascompared with any of the marked pre-existing flaws. The observationswere recorded. The pouches were cut open, emptied, and rinsed with soapand water. One or more one-inch (2.54 cm) strips were cut from thepouches and the laminate bond strength was measured according to thestandard bond strength test described above. This was done as soon aspossible after removing the pouch contents. The interior of the poucheswas examined visually and any visual defects were recorded.

Retort Regulatory Sample Preparation

The pouches consisting of 30.8 square inches (in²) (198.7 squarecentimeters (cm²) of laminate each were filled with 100 mL 3% aceticacid per sample. The pouches were then transferred to the retort chamberwhere they were stored for 2 hr at 121° C. After testing and uponcooling to ambient temperature, the acetic acid was transferred topolyethylene bottles.

The acetic acid samples were extracted and prepared for analysis withindays of preparation and analyzed via liquid chromatography/massspectrometry (LC/MS) within 24 hr of preparation.

The above testing and measurement procedures were performed on thevarious samples prepared as described above. Table IV describes theperformance of such samples.

TABLE IV Performance of Film Samples Example No. Inv. Ex. Inv. Ex. Inv.Ex. Inv. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Inv. Ex. Comp. Comp. Comp. 5 6 78 9 10 11 12 Ex. D Ex. E Ex. F Foil// Foil// Foil// Foil// Foil// Foil//Foil// Foil// Foil// Foil// Foil//

Description Ad* Ad Ad Ad Ad Ad Ad Ad A4// Ad A5// Ad A5// Ad A6// AdA7// of sample A1//CPP A2//CPP A3//CPP A4//CPP A1//CPP A2//CPP A3//CPPCPP CPP CPP CPP CPP Green bond 683; AS 794; AS 740; AS 763; AS 683; AS794; AS 740; AS 763; AS 563; AS 563; AS 533; AS 775, AS (g/25 mm) Drybond 1,269; 1,254; 1,590; 1382; 1,540; 1,626; 1,601; 1,689; 1,053;1,663; 1,468; 1,596; before retort AT AT AT AT AT AT AT AT AT AT AT ATtesting (g/25 mm) Bond after 901; AT 950; AT 1212; AT 911; AT 959; AT1,156; AT 1,288; AT 1301; AT 380; AT 272; 194; 1,116; 1 hr of retort ATAT AT testing at 121° C. (g/25 mm) MDA level 0 0 7.85 7.22 0 0 8.04 9.740 0 35.70 32.03 after 2 hr of retort testing at 121° C. (PPb) CuringTime 7 days at 5 days at 7 days at 5 days at 3 days at 3 days at 3 daysat 3 days at 21 days at 10 days at 3 days at 3 days at 25° C. 25° C. 25°C. 25° C. 50° C. 50° C. 50° C. 50° C. 25° C. 50° C. 50° C. 50° C. *“Ad”stands for “adhesive”.

indicates data missing or illegible when filed

For solvent based adhesives, Inv. Ex. 5 to Inv. Ex. 12 demonstrateexcellent chemical and temperature resistance. In addition, the Inv. Ex.demonstrate fast curing properties and generated no MDA levels or verylow MDA levels after severe retort testing conditions (e.g., <20 ppbafter only 3 days of curing at 50° C.).

OTHER EMBODIMENTS

In one embodiment, the present invention includes a solvent-based retortadhesive composition comprising: (A) at least one isocyanate compound,Component A; and (B) at least one isocyanate-reactive component,Component B; comprising: (i) at least one phosphate ester compound and(ii) at least one polyester polyol having an average molecular weight ofgreater than or equal to 3,000 g/mol.

In another embodiment, the at least one isocyanate compound, Component Aof the adhesive, is at least one aliphatic-based isocyanate. And inanother embodiment, the at least one aliphatic-based isocyanate isselected from the group consisting of xylylene diisocyanate-basedpolyisocyanate, H₆XDI-based polyisocyanate, xylylene diisocyanateisocyanurate, hexamethylene diisocyanate-based polyisocyanate,diisocyanatodicyclohexylmethane-based polyisocyanate, hexamethylenediisocyanate isocyanurate, and mixtures thereof.

In another embodiment, the at least one isocyanate compound, Component Aof the adhesive, is a blend of (i) at least one aliphatic-basedisocyanate and (ii) at least one aromatic-based isocyanate. And, inanother embodiment, the at least one aliphatic-based isocyanate,component (i) of Component A of the adhesive, is selected from the groupconsisting of the aliphatic-based described above; and the at least onearomatic-based isocyanate, component (ii) of Component A of theadhesive, is selected from the group consisting of 1,3- and1,4-phenylene diisocyanate, 1,5-naphthylene diisocyanate, 2,6-tolulenediisocyanate, 2,4-tolulene diisocyanate, 2,4′-diphenylmethanediisocyanate, 4,4′-diphenylmethane diisocyanate,3,3′-dimethyl-4,4′-biphenyldiisocyanate, polymeric isocyanates, andmixtures thereof.

In another embodiment, the at least one aromatic-based isocyanate,component (ii) of Component A of the adhesive, is an isocyanateprepolymer comprising a reaction product of (α) at least one isocyanatecompound and (β) at least one polyol compound. And, in anotherembodiment, the at least one isocyanate compound, component (α), isselected from the group consisting of aromatic polyisocyanates,aliphatic polyisocyanates, cycloaliphatic polyisocyanates, and mixturesthereof. And, in another embodiment, the polyol compound, component (β),is selected from the group consisting of a polyether polyol, a polyesterpolyol, a polycaprolactone polyol, a polyacrylate, a polycarbonatepolyol, a natural oil-based polyol, and mixtures thereof.

In another embodiment, the isocyanate content of the at least oneisocyanate compound, Component A, without solvent is from 1 weightpercent to 25 weight percent.

In another embodiment, the at least one phosphate ester compoundcomponent (i) of Component B of the adhesive, is selected from the groupconsisting of: a phosphate ester compound having the following Structure(I):

wherein R¹ is an organic group, wherein R¹ may or may not have one ormore additional pendant —OH groups, wherein R¹ may or may not have oneor more additional pendant groups of Structure (I), and wherein two ormore of the —OH groups and the group(s) of Structure (I) may or may notbe attached to the same atom of R¹; a phosphate ester compoundcontaining urethane linkages; and mixtures thereof. And, in anotherembodiment, the content of the at least one phosphate ester compound,component (i) of Component B of the adhesive, is from 0.1 weight percentto 30 weight percent.

In another embodiment, the at least one polyester polyol, component (ii)of Component B of the adhesive, is selected from the group consisting ofaliphatic polyester polyols, aromatic polyester polyols, copolymers ofaliphatic and aromatic polyester polyols, polycarbonate polyols,polycaprolactone polyols, and mixtures thereof.

In another embodiment, the at least one polyester polyol, component (ii)of Component B of the adhesive, is: (1) the reaction product of apolybasic acid and a polyhydric alcohol, (2) the reaction product ofphosgene or a carbonate monomer with a polyhydric alcohol; or (3)produced via ring opening polymerization of cyclic ester compounds.

In another embodiment, the at least one isocyanate-reactive component,Component B of the adhesive, includes further (iii) at least onepolyether polyol having an average molecular weight less than 1,500g/mol.

In another embodiment, the at least one polyether polyol, component(iii) of Component B of the adhesive, is selected from group consistingof polypropylene glycols, polytetramethylene ether glycols, polybutyleneoxide-based polyols, mixtures thereof, and copolymers thereof.

In another embodiment, the adhesive of the present invention furthercomprises: (C) a solvent selected from the group consisting of ethylacetate, methyl ether ketone, toluene, and mixtures thereof.

In another embodiment, the adhesive of the present invention, furthercomprises: (D) an additive selected from the group consisting of acatalyst, a surfactant, a leveling agent, a defoamer, a rheologymodifier, a color pigment, and mixtures thereof.

What is claimed is:
 1. A solvent-based retort adhesive compositioncomprising: (A) at least one isocyanate compound, Component A; and (B)at least one isocyanate-reactive component, Component B; comprising: (i)at least one phosphate ester compound and (ii) at least one polyesterpolyol having an average molecular weight of greater than or equal to3,000 g/mol.
 2. The adhesive of claim 1, wherein the at least oneisocyanate compound, Component A, is at least one aliphatic-basedisocyanate; or wherein the at least one isocyanate compound, ComponentA, is a blend of (i) at least one aliphatic-based isocyanate and (ii) atleast one aromatic-based isocyanate.
 3. The adhesive of claim 2, whereinthe at least one aromatic-based isocyanate, component (ii) of ComponentA, is an isocyanate prepolymer comprising a reaction product of (α) atleast one isocyanate compound and (β) at least one polyol compound. 4.The adhesive of claim 1, wherein the at least one phosphate estercompound component (i) of Component B, is selected from the groupconsisting of: a phosphate ester compound having the following Structure(I):

wherein R¹ is an organic group, wherein R¹ may or may not have one ormore additional pendant —OH groups, wherein R¹ may or may not have oneor more additional pendant groups of Structure (I), and wherein two ormore of the —OH groups and the group(s) of Structure (I) may or may notbe attached to the same atom of R¹; a phosphate ester compoundcontaining urethane linkages; and mixtures thereof.
 5. The adhesive ofclaim 1, wherein the at least one polyester polyol, component (ii) ofComponent B, is selected from the group consisting of aliphaticpolyester polyols, aromatic polyester polyols, copolymers of aliphaticand aromatic polyester polyols, polycarbonate polyols, polycaprolactonepolyols, and mixtures thereof.
 6. The adhesive of claim 1, wherein theat least one isocyanate-reactive component, Component B, includesfurther (iii) at least one polyether polyol having an average molecularweight less than 1,500 g/mol.
 7. A process for producing a solvent-basedpolyurethane retort adhesive composition for producing laminatescomprising admixing: (A) at least one isocyanate compound, Component A;and (B) at least one isocyanate reactive component, Component B,comprising: (i) at least one phosphate ester compound and (ii) at leastone polyol comprising a polyester polyol having an average molecularweight of greater than or equal to 3,000 g/mol.
 8. A multi-layerlaminate product comprising: (a) at least a first layer; (b) at least asecond layer; and (c) the retort adhesive of claim 1 disposed inbetweenthe first layer and the second layer; wherein the adhesive is cured tobond the first layer to the second layer.
 9. A process for producing alaminate product comprising the steps of: (I) applying the retortadhesive of claim 1 to at least a portion of the surface of the firstlayer and/or the second layer; (II) contacting the first layer and thesecond layer such that the adhesive is disposed inbetween the firstlayer and the second layer; and (III) curing the adhesive to form alaminate comprising the first layer bonded to the second layer via thecured adhesive.
 10. A container for retort packaging comprising thelaminate of claim 8.